Photochemical and heterogeneous photocatalytic degradation of waste vinylsulphone dyes: a case study with hydrolysed Reactive Black 5

Aqueous solutions of hydrolyzed Reactive Black 5 (RB5) dye, a well-known su rrogate for non-biodegradable azo dyes, were photochemically and photocatal ytically treated by employing the H2O2/W-C and TiO2/UV-A advanced oxidation systems, respectively. The observed effects of reaction pH, oxidant dose a nd initial dyestuff concentration were used to explain the OH. induced colo r disappearance kinetics empirically. Accordingly, the waste dyestuff solut ions could be completely decolorised (k(d.max) = 0.155 min(-1); H2O2/UV-C s ystem) and effectively mineralised (k(TOC.max) = 0.01 min(-1); H2O2/UV-C sy stem), with an average overall TOC removal of 78% after 120 min advanced ox idation at the specified optimised reaction conditions. The treatment via H 2O2/UV-C was mainly governed by OH. type oxidation rather than direct UV-C or UV-A photolysis, and the bleaching effect of the TiO2/UV-A process could be successfully fitted to the empirical Langmuir-Hinshelwood (L-H) kinetic model (k(L-H) = 4.47 mg l(-1) min(-1); KL-H = 2.01 l mg(-1)). (C) Elsevier Science 2001 B.V. All rights reserved.